The present invention relates to a rotary fluid pressure device wherein high pressure fluid is routed from an inlet port through the rotary fluid pressure device to a recess in an externally toothed rotor member in order to overbalance the rotor towards a manifold assembly in order to minimize the leakage of fluid with the rotary fluid pressure device.
The use of rotary fluid pressure devices for motors and pumps is well known in the art. One type of rotary fluid pressure devices is generally referred to as gerotors, gerotor type motors, and gerotor type pumps, hereinafter referred to as gerotor motors. Gerotor motors are compact in size, low in manufacturing cost, have a high-torque capacity ideally suited for such applications as turf equipment, agriculture and forestry machinery, mining and construction equipment, as well as winches, etc. Gerotor motors have gerotor sets which have a special form of internal gear transmission consisting of two main elements: an inner rotor and an outer stator.
The inner rotor and the outer stator possess different centers. The inner rotor has a plurality of external teeth which contacts circular arcs on the interior of the outer stator when it revolves. An output shaft is either directly connected to the orbiting inner rotor or is connected thereto by a drive link splined at each end. When pressurized fluid flows into a motor, the resistance of an external torsional load on the motor begins to build differential pressure, which in turn causes the inner rotor to rotate in the desired direction via a timing valve.
Typically, due to the flow of high pressure fluid through the gerotor sets, namely into and out of the volume chambers in the gerotor set, the inner rotor tends to have an imbalance of forces acting upon it. This imbalance of forces will cause the rotor to tilt to one side during its rotation, resulting in unwanted wearing along the surface of the rotor that comes in contact with an adjacent component, e.g. an end cap. Prior art constructions, such as those set forth in U.S. Pat. No. 5,624,248 to Kassen et al. have used an adjacent component, such as a plate, in order to balance the rotor that has tipped in one direction. The plate has hydraulic forces acting on one side, causing it to flex and come in physical contact with the rotor. This contact offsets the differential of forces which tip the rotor, thus allowing the rotor to rotate uniformly. The gerotor set of the present invention uses pressurized fluid to balance the rotor without having an extra component that physically contacts the rotor.
Gerotor motors are commonly comprised of several aligned components for routing fluid for the purpose of supplying a driving force. The gerotor set has adjacent componentry which directs the pressurized fluid into and out of the rotor. A rotating balanced rotor will be spaced apart from the adjacent componentry, thus allowing gaps and cross-port leakage. One of the components typically adjacent to the gerotor set is a manifold assembly. The interface between the gerotor set and the manifold assembly is a common area for leakage due to the continuous valving of fluid that takes places in this location. Prior art constructions, such as that shown in U.S. Pat. No. 4,717,320 to White, Jr., supply a flexible balancing plate, on the opposite side of the gerotor set from the manifold assembly, for reducing the gap between the gerotor set and the manifold assembly. This prior art construction routes pressurized fluid to the backside of the flexible balancing plate in order to bow the balancing plate physically against the rotor and force the rotor against the manifold assembly. The present invention places a rigid, channeling plate on the opposite side of the gerotor set from the manifold assembly. The channeling plate directs pressurized fluid into a recess in the axial surface of the rotor and biases the rotor towards the manifold assembly. This reduces the gap between the gerotor set and the manifold assembly, thus minimizing the leakage at this interface.
A feature of the present invention is to provide a rotary fluid pressure device comprised of a housing member, a manifold assembly, a gerotor set, a channeling plate, an end plate, and means for routing high pressure fluid from the housing member to the gerotor set. The housing member has a high pressure fluid inlet port, an exhaust fluid outlet port, a first flow passage and an internal bore. The manifold assembly has a first and second fluid passage, and an internal bore with one side of the manifold assembly adjoining the housing member. The gerotor set is positioned next to the manifold assembly and has an internally toothed stator member with at least one axial fluid path extending therethrough, and an externally toothed rotor member eccentrically disposed within the stator member having an internal bore, a first axial end surface, and a second axial end surface having a recess circumferentially surrounding the internal bore. The rotor member includes a plurality of axially extending through holes for fluid flow there through being adapted for hydraulically axially balancing the axial end surfaces of the rotor member relative to the stator member. The channeling plate is positioned between the end plate and the geroter set and has a first side, a second side, a first fluid passage extending therethrough, a second fluid passage extending therethrough, and a plurality of through holes. A cavity is located between the channeling plate and the end plate and receives high pressure fluid. The high pressure fluid routing means directs fluid from one of the housing member""s first and second flow passages, through the at least one axial fluid path within the stator member, through the rotor member internal bore, through one of channeling plate""s first and second fluid passages, into and subsequently out of the cavity, through the plurality of through holes in the channeling plate, and into the recess in the second axial end surface of the rotor. The high pressure fluid within the recess overbalances the previously axially balanced rotor axially towards the manifold assembly.
In the noted rotary fluid pressure device, the recess can be comprised of multiple convolutions, and the at least one of the plurality of through holes in the channeling plate is axially aligned at all time with the recess during each complete 360xc2x0 hypocycloidal movement of the rotor. Further in the noted rotary fluid pressure device, the recess can be generally circular. Also in the noted rotary pressure device, the cavity can be located within and concentric with the channeling plate. Further, the cavity could be located within and concentric with the end plate.
Another feature of the noted rotary fluid pressure device includes having the first fluid passage of the manifold assembly being axially aligned with the at least one axial fluid path in the stator member. An additional feature of the noted rotary fluid pressure device includes having the second fluid passage of the manifold assembly being axially aligned with the internal bore of the rotor member.
A further feature of the noted rotary fluid pressure device has the means for routing of the high pressure fluid including a first check valve located with the channeling plate first fluid passage and a second check valve located within the channeling plate second fluid passage.
Another feature of the present invention includes a rotary fluid pressure device similar to the previously noted device wherein the housing member has a fluid inlet port and a first flow passage for receiving one of a high pressure fluid and an exhaust fluid, a fluid outlet port and second flow passage for receiving the other of the high pressure fluid and the exhaust fluid, and an internal bore for receiving one of the high pressure fluid and the exhaust fluid. The manifold assembly has a first fluid passage fluidly connected with the housing member first flow passage for receiving one of the high pressure fluid and the exhaust fluid, a second fluid passage fluidly connected with the housing member second flow passage for receiving the other of the high pressure fluid and the exhaust fluid, and an internal bore fluidly connected with the housing member internal bore for receiving one of the high pressure fluid and the exhaust fluid. The gerotor set has an internally toothed stator member with at least one axial fluid path extending therethrough fluidly connected with the manifold assembly first flow passage for receiving one of the high pressure fluid and the exhaust fluid, and an externally toothed rotor member hydraulically balanced relative to the stator, eccentrically disposed within the stator member, having an internal bore fluidly connected with the manifold assembly second fluid passage for receiving the other of the high pressure fluid and the exhaust fluid. The rotor member also including a first axial end surface, a second axial end surface including a recess circumferentially surrounding the internal bore for receiving the high pressure fluid, and a plurality of axially extending through holes for receiving one of the high pressure fluid and the exhaust fluid. The channeling plate being substantially rigid and having a first side, a second side, a first fluid passage fluidly connected with the stator member at least one axial fluid path. The first fluid passage extending through the channeling plate for receiving one of the high pressure fluid and the exhaust fluid. The channeling plate also including a second fluid passage, fluidly connected with the rotor internal bore, extending through the channeling plate for receiving the other of the high pressure fluid and the exhaust fluid, and a plurality of through holes fluidly connected with the rotor second axial end surface recess for receiving the high pressure fluid. The end plate has a first side adjacent the second side of the channeling plate. The cavity being fluidly connected with the plurality of through holes in the channeling plate, located between the channeling plate and the end plate for receiving the high pressure fluid from one of either the channeling plate first and second fluid passages.
A further feature of the noted rotary fluid pressure device includes having the channeling plate with a first check valve located with the first fluid passage and a second check valve located with the second fluid passage. Also, an additional feature includes having one of the first and second check valves opening for allowing high pressure flow to pass therethrough. Another feature includes having the cavity being located with and concentric with one of the channeling plate and the end plate.